Autopulse

One way you can usually tell if a 550 Spyder is authentic is by its original duel Autopulse fuel pumps fitted in the driver’s side cavity underneath the fuse box. The series 500 pumps were manufactured by Walbro Corp in the USA are still readily available second hand today as they were extensively used on trucks and early model American cars. Interestingly enough they were chosen by Porsche for their reliability as the two 6 volt mechanical pumps were joined together using a pair of manifolds which was necessary to overcome fuel inertia in forward and upward acceleration. These were connected by a fuel line in from the long range fuel tank used in races like 24 hour LeMans and 12 hour Sebring, to the quad cam engine situated behind the driver, to ensure a constant flow was maintained. Today, complete sets are highly sought after with the manifolds and banjo screws being a prized find. Most replicas with the Autopulse fuel pumps connected are only for show and not functional as the 6 volt will not run on the modern 12 volt cars.

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